0 ≤ i ⊦ i % 2 = 0 ↔ ¬(∃ i0. i = 2 * i0 + 1)
⊦ i % 2 = 0 ↔ ¬(∃ i0. i = 2 * i0 + 1), 0 ≤ i
Used formulas: 0 ≤ i